DWR3-ReverseAjax-半推实现

编程技术  /  houtizong 发布于 3年前   68

第一次发帖，直奔主题。

 

首先，配置web.xml加入参数开启ReverseAjax

<servlet><servlet-name>dwr</servlet-name><servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class><init-param><param-name>activeReverseAjaxEnabled</param-name><param-value>true</param-value></init-param><init-param>    <param-name>initApplicationScopeCreatorsAtStartup</param-name>    <param-value>true</param-value>  </init-param>  <init-param><param-name>org.directwebremoting.extend.ScriptSessionManager</param-name><param-value>com.cssweb.business.dwr.CustomSSManager</param-value></init-param>  <load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>dwr</servlet-name><url-pattern>/dwr/*</url-pattern></servlet-mapping>

   注意红色部分，即半推实现方式：加入自己的ScriptSessionManager.由于dwr每次刷新激活ReverseAjax的页面都会创建一个ScriptSession，这里要自己管理它以便实现半推，同时和HttpSession做同步，以最后请求的ScriptSession为准，销毁之前的ScriptSession。

下面就是CustomSSManager：

import java.util.Collection;import javax.servlet.http.HttpSession;import org.directwebremoting.ScriptSession;import org.directwebremoting.WebContextFactory;import org.directwebremoting.event.ScriptSessionEvent;import org.directwebremoting.event.ScriptSessionListener;import org.directwebremoting.impl.DefaultScriptSession;import org.directwebremoting.impl.DefaultScriptSessionManager;import com.cssweb.business.user.pojo.User;import com.cssweb.constans.CONST;/** *  * 扩展ScriptSessionManager. * @author congyy * @createTime   2010-1-3            */public class CustomSSManager extends DefaultScriptSessionManager {        public static final String SS_ID = "DWR_ScriptSession_Id";        public CustomSSManager() {             addScriptSessionListener(new ScriptSessionListener(){                public void sessionCreated(ScriptSessionEvent event) {                        ScriptSession scriptSession = event.getSession(); // 获取新创建的SS                        HttpSession httpSession  = WebContextFactory.get().getSession();// 获取构造SS的用户的HttpSession                        User user = (User)httpSession.getAttribute(CONST.SESSION_USER);                        if(user ==null){                                scriptSession.invalidate();                                httpSession.invalidate();                                return;                        }                        String ssId = (String) httpSession.getAttribute(SS_ID);                        if (ssId != null) {                                DefaultScriptSession old=sessionMap.get(ssId);                               if(old!=null)CustomSSManager.this.invalidate(old);                        }                        httpSession.setAttribute(SS_ID, scriptSession.getId());                        scriptSession.setAttribute("userId", user.getId());//此处将userId和scriptSession绑定                }                public void sessionDestroyed(ScriptSessionEvent event) {}             });           ReqReverseAjax.manager=this;//将自己暴露ReverseAjax业务处理类        }        public Collection getAllScriptSessions(){                return sessionMap.values();        }}

 关于上述代码 ：User为POJO类，CONST为常量放置接口,如session中的用户KEY.

 然后是ReverseAjax业务处理类：

package com.cssweb.business.dwr;import java.util.Collection;import java.util.Observable;import java.util.Observer;import org.directwebremoting.ScriptBuffer;import org.directwebremoting.ScriptSession;import org.directwebremoting.extend.ScriptSessionManager;import com.cssweb.business.user.pojo.UserReq;import com.cssweb.business.user.service.IUserReqService;/** * Observer实现，监听事件，然后推送给指定用户. */public class ReqReverseAjax implements Observer{  static ScriptSessionManager manager ;  public ReqReverseAjax() {          IUserReqService.GCZ.addObserver(this);//注册观察者  }  public void update(Observable o, Object arg) {        final UserReq req = (UserReq) arg;        final Long userId = req.getToId();//获取事件要通知的用户的id        Collection<ScriptSession>  coll = manager.getAllScriptSessions();//获取当前所有ScriptSession        for(ScriptSession ss : coll) {             if(ss.getAttribute("userId").equals(userId)){                     ss.addScript(new ScriptBuffer().appendScript("update").appendScript("(").appendData(req).appendScript(");"));//找到符合要求的，推送事件                     break;             }        }   }}

 然后在WEB-INF/下丢一个dwr.xml：

 

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN" "http://getahead.org/dwr/dwr30.dtd"><dwr>  <allow>    <create creator="new" scope="application">      <param name="class" value="com.cssweb.business.dwr.ReqReverseAjax"/>    </create>    <convert converter="bean" match="com.cssweb.business.user.pojo.UserReq"/>  </allow></dwr>

 至此，服务端配置完全结束，实现半推。

 页面上实现如下：

  index.jsp，加上框架，减少对reverseAjax.html页面的刷新量

<%@ page  pageEncoding="UTF-8"%><frameset rows="*" cols="0,*" border="0"><frame src="${contextPath }/jsp/ajax/user/reverseAjax.html#${contextPath }" frameborder="0"><frame src="${contextPath }/jsp/user/index.do"/></frameset>

 

reverseAjax.html:

<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><script type="text/javascript"> function update(req) { //在这里处理服务器推过来的信息 } var url = self.location.href; var ctx = url.slice(url.indexOf('#')+1); document.write("<script src='"+ctx+"/dwr/engine.js'><\/script>"); </script></head><body onload="dwr.engine.setActiveReverseAjax(true)"></body></html>

 好了，至此半推结束.